This invention relates to biomedical electrodes, that is, electrodes to be used for examinations or treatments in which an electrode member is electrically connected with the skin of a patient. Examples of electrodes of this kind are ECG and EEG electrodes.
The biomedical electrodes with which the invention is concerned preferably are so-called suction electrodes. Such electrodes are held to the skin by vacuum in a chamber which is delimited on the skin by a sealing device resembling a suction cup in which the electrode member is positioned. Accordingly, the invention will be described with particular reference to its use in connection with suction electrodes.
More particularly, the invention relates to a contact or interface element for use in a biomedical electrode, especially a vacuum electrode, which element is of the kind defined in the precharacterising portion of claim 1. A contact or interface element of this kind is known from GB-A-2 240 928. This known element is intended only for use with adhesive electrodes and does not lend itself to use with suction electrodes.
Moreover, the invention relates to a method for carrying out biomedical measurements using suction electrodes.
Especially when carrying out measurements using biomedical electrodes it is important have a low impedance in the electrical connection between the skin and the electrode member, but even more important is that the connection is stable throughout the measuring process in respect of the electrical properties. If variations of the electrical properties occur, they will have an adverse influence on the measuring signals.
Such variations are particularly difficult to avoid when suction electrodes are used. This is because the signals are picked up not only from the skin area engaged by the contact face of the electrode member, but also from the surrounding area, especially if sweat and electrolyte form a layer under and around the electrode member. When suction electrodes are used it is almost impossible to prevent air from leaking inwardly between the skin and the edge of the sealing device. Air that leaks in may form bubbles which migrate from the periphery of the sealing device and inwardly along the skin toward the centrally positioned electrode element and cause variations of the electrical conductivity, and possibly also dipole variations if electrostatic fields exist around the electrode member.
One proposed solution to the problem caused by the aforesaid variations involves a special design of the sealing device.